Carrier aggregation scell selection for lte-a

ABSTRACT

Systems and methods for Secondary Cell (sCell) selection for wireless devices operating according to a carrier aggregation scheme in a cellular communications network are disclosed. In one embodiment, a network node obtains a list of potential sCells for a wireless device. The network node blindly selects an sCell for the wireless device from the list of potential sCells. The network node then configures the wireless device with the selected sCell. Blindly selecting the sCell for the wireless device makes it possible to avoid the use of measurement gaps and reduce throughput loss, according to some embodiments.

RELATED APPLICATIONS

This application claims the benefit of provisional patent applicationSer. No. 61/880,689, filed Sep. 20, 2013, the disclosure of which ishereby incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to a cellular communications network, andmore particularly relates to secondary cell selection for wirelessdevices operating according to a carrier aggregation scheme.

BACKGROUND

Carrier aggregation was introduced in 3^(rd) Generation PartnershipProject (3GPP) Long Term Evolution (LTE) Advanced Release 10 (LTERel-10) as an LTE-Advanced feature. Using carrier aggregation, multiplecomponent carriers (CCs) can be aggregated and jointly used fortransmission to or from a single wireless device. Each component carriercan have any of the LTE Release 8 (LTE Rel-8) bandwidths: 1.4, 3, 5, 10,or 20 Megahertz (MHz). Up to five component carriers can be aggregatedto give a maximum aggregated bandwidth of 100 MHz. Further, eachcomponent carrier uses the LTE Rel-8 structure to provide backwardcompatibility (i.e., each component carrier appears as an LTE Rel-8carrier).

FIG. 1 illustrates one example of carrier aggregation. In this example,cells 10-0 through 10-4, having carrier frequencies F0, F1, F2, F3, andF4, respectively, can be aggregated. In this example, the cells 10-0through 10-4 are transmitted by a single base station 12. With respectto a particular wireless device, one of the cells 10-0 through 10-4serves as a Primary Cell (pCell) of the wireless device, where the pCellhandles Radio Resource Control (RRC) connection. The component carrierof the pCell is referred to as the Primary Component Carrier (PCC).Other cells aggregated with the pCell for the wireless device arereferred to as Secondary Cells (sCells) having corresponding SecondaryComponent Carriers (SCCs). All of the aggregated cells for the wirelessdevice are referred to as serving cells of the wireless device.

The coverage areas of the cells 10-0 through 10-4 may differ either dueto different component carrier frequencies or due to power planning onthe different component carriers. In the example of FIG. 1, the cell10-0 has the largest coverage area and serves as the pCell for wirelessdevices A, B, C, D, and F located in the cell 10-0. The cells 10-1through 10-4 have successively smaller coverage areas and serve assCells for wireless devices B through F. In this example, the wirelessdevice A has no sCell coverage, the wireless device B has sCell coveragefor one sCell (namely cell 10-1), the wireless device C has sCellcoverage for two sCells (namely cells 10-1 and 10-2), the wirelessdevice D has sCell coverage for three sCells (namely cells 10-1, 10-2,and 10-3), and the wireless device F has sCell coverage for four sCells(namely cells 10-1, 10-2, 10-3, and 10-4). Therefore, depending on theposition of a wireless device within the pCell, the wireless device mayhave no sCell coverage or may have coverage of one or more sCells.

For a wireless device connected to the pCell on carrier frequency F0(e.g., wireless device A), the base station 12 normally startsinter-frequency layer 3 (L3) measurements on candidate sCell(s) in orderto determine whether the wireless device has any sCell coverage. Forinstance, the base station 12 normally starts inter-frequency L3measurements such as, for example, a measurement that triggers an A4event when the inter-frequency L3 measurement for an sCell becomesbetter than a threshold. In the LTE specifications, an A4 event occurswhen a neighboring cell becomes better than a threshold, which isreferred to herein as an A4 threshold. In the example of FIG. 1, with aproper A4 threshold, an A4 event will trigger on carrier frequency F1for the wireless device B to thereby indicate that the wireless device Bhas sCell coverage via the cell 10-1. In contrast, for the wirelessdevice F, an A4 event will trigger on carrier frequencies F1, F2, F3,and F4 to thereby indicate that the wireless device F has sCell coveragevia cells 10-1, 10-2, 10-3, and 10-4. Based on the measurement eventtriggering, one or more sCells are selected and configured for eachwireless device having sCell coverage.

One issue with this normal sCell selection process is that theinter-frequency measurements may require measurement gaps. Measurementgaps are periods during which there is no traffic in both the uplink anddownlink directions. Using measurement gaps to perform theinter-frequency measurements for sCell selection will incur 7-15%throughput loss on configured cells depending on the gap patternconfigured.

Another issue with the normal sCell selection process is that to performany measurements (inter-frequency or intra-frequency, gap or gaplessmeasurements) on the candidate sCells, the parameter s-Measure may haveto be disabled. As defined in the LTE specifications, when the pCell'sReference Signal Received Power (RSRP) measurement is not belows-Measure, the wireless device is not required to perform any neighborcell measurements, including the measurements on the candidate sCell(s),in order to save battery power. Thus, in order to guarantee that themeasurements on the candidate sCell(s) are being performed by thewireless devices A, B, C, D, and F when using the normal sCell selectionprocess, the s-Measure parameter will have to be disabled, which willcause increased wireless device battery consumption.

In light of the discussion above, there is a need for systems andmethods for improved sCell selection.

SUMMARY

Systems and methods for Secondary Cell (sCell) selection for wirelessdevices operating according to a carrier aggregation scheme in acellular communications network are disclosed. In one embodiment, anetwork node obtains a list of potential sCells for a wireless device.The network node blindly selects an sCell for the wireless device fromthe list of potential sCells. The network node then configures thewireless device with the selected sCell. Blindly selecting the sCell forthe wireless device can avoid the use of measurement gaps and reducethroughput loss, according to some embodiments.

In one embodiment, blindly selecting the sCell includes selecting thesCell from the list of potential sCells based on a round-robin strategy.Further, in one embodiment, the round-robin strategy is started in thelist of potential sCells at a position in the list that is differentfrom a position at which a previous iteration of the round-robinstrategy for selecting a previous sCell stopped. In another embodiment,the round-robin strategy is started in the list of potential sCells at aposition in the list immediately succeeding a position at which aprevious iteration of the round-robin strategy for selecting a previoussCell stopped. In still another embodiment, blindly selecting the sCellincludes selecting the sCell from the list of potential sCells based ona random selection strategy.

In one embodiment, after the network node configures the wireless devicewith the selected sCell, the network node receives an indication fromthe wireless device that a neighboring cell of the selected sCell isbetter than the selected sCell. In response to receiving the indication,the network node configures the wireless device with the neighboringcell as an sCell of the wireless device. Further, in one embodiment, thenetwork node deconfigures the selected sCell as an sCell of the wirelessdevice. In one embodiment, the indication is an indication of an A4event. In another embodiment, the indication is an indication of an A6event.

In one embodiment, after configuring the wireless device with theselected sCell, the network node receives an indication from thewireless device that the selected sCell is not an acceptable sCell forthe wireless device. In response, the network node blindly selects a newsCell for the wireless device from the list of potential sCells for thewireless device. The network node then configures the wireless devicewith the new sCell selected for the wireless device. In one embodiment,the network node deconfigures the selected sCell as an sCell of thewireless device. In one embodiment, the indication is an indication ofan A2 event.

In one embodiment, after configuring the wireless device with theselected sCell, the network node receives an indication from thewireless device that the selected sCell is not an acceptable sCell forthe wireless device. In response, the network node monitors for anindication from the wireless device that a neighboring cell of theselected sCell is better than the selected sCell. If the indication thatthe neighboring cell of the selected sCell is better than the selectedsCell is not received within a defined period of time, the network nodeblindly selects a new sCell for the wireless device from the list ofpotential sCells for the wireless device. This blind selection excludespotential sCells that operate at a frequency that is the same as afrequency of operation of the selected sCell. The network node thenconfigures the wireless device with the new sCell selected for thewireless device. In one embodiment, the indication from the wirelessdevice that the selected sCell is not an acceptable sCell for thewireless device is an indication of an A2 event and the indication thatthe neighboring cell of the selected sCell is better than the selectedsCell is an indication of an A4 event or an A6 event.

In one embodiment, the list of potential sCells is sorted by a frequencyof operation of the potential sCells to thereby provide a plurality offrequency groups within the list. Also, blindly selecting the sCellincludes blindly selecting the sCell from one frequency group accordingto a round-robin strategy. After configuring the wireless device withthe selected sCell, the network node receives an indication from thewireless device that the selected sCell is not an acceptable sCell forthe wireless device. In response, the network node monitors for anindication from the wireless device that a neighboring cell of theselected sCell is better than the selected sCell. If the indication thatthe neighboring cell of the selected sCell is better than the selectedsCell is not received within a defined period of time, the network nodeblindly selects a new sCell for the wireless device from a nextfrequency group in the list of potential sCells according to theround-robin strategy. The network node then configures the wirelessdevice with the new sCell selected for the wireless device.

In one embodiment, after configuring the wireless device with theselected sCell, the network node monitors for at least one indicationfrom the wireless device. The at least one indication can be anindication that the selected sCell is an acceptable sCell for thewireless device, an indication that the selected sCell is not anacceptable sCell for the wireless device, or an indication that aneighboring cell of the selected sCell is better than the selectedsCell. If the at least one indication is not received within a definedperiod of time, the network node blindly selects a new sCell for thewireless device from the list of potential sCells for the wirelessdevice. The network node then configures the wireless device with thenew sCell selected for the wireless device.

In one embodiment, obtaining the list of potential sCells includesdetermining the list based on an intersection of cells available to beconfigured as an sCell and capabilities of the wireless device. Further,in one embodiment, the list of potential sCells is determined based onan intersection of a frequency of operation of cells available to beconfigured as an sCell and frequency capabilities of the wirelessdevice.

In one embodiment, the list of potential sCells for the wireless deviceincludes potential sCells in an order that is different from an order ofpotential sCells comprising a second list of potential sCells for asecond wireless device.

In one embodiment, the network node weights the list of potential sCellsbefore blindly selecting the sCell. Further, in one embodiment,weighting the list of potential sCells before blindly selecting thesCell includes adding one or more duplicate entries into the list ofpotential sCells. In another embodiment, weighting the list of potentialsCells before blindly selecting the sCell includes adjusting aprobability of selection for one or more entries in the list ofpotential sCells.

In one embodiment, the network node is a radio network node. Further, inone embodiment, the radio network node is a base station.

In one embodiment, a network node for configuring a wireless device withan sCell includes a processor and a memory. The memory containsinstructions executable by the processor. By executing the instructions,the network node is operative to obtain the list of potential sCells forthe wireless device. The network node is also operative to blindlyselect an sCell for the wireless device from the list of potentialsCells. The network node is also operative to configure the wirelessdevice with the selected sCell.

Those skilled in the art will appreciate the scope of the presentdisclosure and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the disclosure, andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 illustrates one example of carrier aggregation in a cellularcommunications network;

FIG. 2 illustrates a cellular communications network in which a basestation performs Secondary Cell (sCell) selection for wireless devicesaccording to one embodiment of the present disclosure;

FIG. 3 illustrates the operation of a network node for configuring awireless device with an sCell according to one embodiment of the presentdisclosure;

FIG. 4 illustrates the operation of a network node, including receivingan indication regarding a neighboring cell of a selected sCell accordingto one embodiment of the present disclosure;

FIG. 5 illustrates the operation of a network node, including receivingan indication that a selected sCell is not acceptable according to oneembodiment of the present disclosure;

FIG. 6 illustrates the operation of a network node, including theexclusion of potential sCells that operate at a frequency that is thesame as a frequency of operation of a selected sCell according to oneembodiment of the present disclosure;

FIG. 7 illustrates the operation of a network node based on around-robin strategy according to one embodiment of the presentdisclosure;

FIG. 8 illustrates the operation of a network node, including specificevents according to one embodiment of the present disclosure;

FIG. 9 is a block diagram of a network node according to one embodimentof the present disclosure;

FIG. 10 is a block diagram of a wireless device according to oneembodiment of the present disclosure; and

FIG. 11 is a block diagram of a radio access node for configuring awireless device with an sCell according to one embodiment of the presentdisclosure.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the embodiments andillustrate the best mode of practicing the embodiments. Upon reading thefollowing description in light of the accompanying drawing figures,those skilled in the art will understand the concepts of the disclosureand will recognize applications of these concepts not particularlyaddressed herein. It should be understood that these concepts andapplications fall within the scope of the disclosure and theaccompanying claims.

Systems and methods for Secondary Cell (sCell) selection for wirelessdevices operating according to a carrier aggregation scheme in acellular communications network are disclosed. In one embodiment, anetwork node obtains a list of potential sCells for a wireless device.The network node blindly selects an sCell for the wireless device fromthe list of potential sCells. The network node then configures thewireless device with the selected sCell. Blindly selecting the sCell forthe wireless device can avoid the use of measurement gaps and reducethroughput loss, according to some embodiments.

In this regard, FIG. 2 illustrates a cellular communications network 14in which sCell selection is performed according to one embodiment of thepresent disclosure. Note that in many of the embodiments describedherein, the cellular communications network 14 is a 3^(rd) GenerationPartnership Project (3GPP) Long Term Evolution (LTE) or LTE-Advancedcellular communications network and, as such, LTE or LTE-Advancedterminology is sometimes used. However, the concepts disclosed hereincan be applied to any suitable wireless network (e.g., cellularcommunications network) that utilizes carrier aggregation and in whichsCell selection is desired.

As illustrated, the cellular communications network 14 includes a basestation 16, which in LTE terminology is referred to an evolved Node B(eNB) 16, and a number of Remote Radio Heads (RRHs) 18-1 through 18-3(generally referred to herein collectively as RRHs 18 and individuallyas RRH 18). The RRHs 18 are RRHs of the base station 16. In thisexample, the base station 16 serves a cell that is a serving cell, andmore particularly a Primary Cell (pCell) 20, for a wireless device 22located within a coverage area of the pCell 20. As used herein, thecoverage area of a cell (e.g., the coverage area of the pCell 20) is ageographic area covered by the cell. Cells of the RRHs 18-1 through 18-3are sCells 24-1 through 24-3 (generally referred to herein collectivelyas sCells 24 and individually as sCell 24) may be small cells, accordingto one embodiment. As discussed below, one or more of the sCells 24 areselected and configured as serving sCells 24 of the wireless device 22.Note that while the macro cell 20 is the pCell in this example, themacro cell 20 may, in another example, be an sCell. For instance, usingthe wireless device 22 as an example, the small cell 24-2 mayalternatively be the pCell for the wireless device 22 and the macro cell20 may alternatively be an sCell for the wireless device 22.

FIG. 3 illustrates the operation of a network node for selecting one ormore of the sCells 24 for the wireless device 22 and configuring thewireless device 22 with the selected sCell(s) 24 according to oneembodiment of the present disclosure. The network node may be anysuitable network node (e.g., the base station 16, any suitable radioaccess network node, or any suitable core network node (e.g., a mobilitymanagement entity)). First, the network node obtains a list of potentialsCells 24 for the wireless device 22 (step 100). This list of potentialsCells 24 can be obtained in several ways. In one embodiment, thenetwork node obtains a list of cells (e.g., neighboring cells) that areavailable to be configured as sCells 24 and capabilities of the wirelessdevice 22. The network node then obtains the list of potential sCells 24based on an intersection of cells available to be configured as an sCell24 and the capabilities of the wireless device 22 (i.e., the list ofpotential sCells 24 is a list of cells that are both available to beconfigured as sCells 24 and have one or more parameters (e.g., frequencyband or frequency of operation) that match the capabilities of thewireless device 22 (e.g., frequency band(s) or frequency(ies) ofoperation of the wireless device 22). The network node may have manycells, but not all of the cells may necessarily be available to be usedas sCells 24. Furthermore, although wireless devices 22 are increasinglysupporting more frequencies, there are often still frequencies that arenot supported by a given wireless device 22.

After obtaining the list of potential sCells 24, the network node mayoptionally weight the list of potential sCells 24 (step 102). Thisweighting serves to make the selection of one or more sCells 24 morelikely and/or to make the selection of one or more sCells 24 lesslikely. This can be accomplished in various ways depending on theparticular implementation. In one embodiment, weighting the list ofpotential sCells 24 includes adding one or more duplicate entries intothe list of potential sCells 24. In another embodiment, weighting thelist of potential sCells 24 before blindly selecting the sCell 24includes adjusting a probability of selection for one or more entries inthe list of potential sCells 24.

Next, the network node blindly selects an sCell 24 for the wirelessdevice 22 from the list of potential sCells 24 (step 104). As usedherein, “blindly selecting” means that the sCell 24 is selected withoutnecessarily having any indication of the sCell's suitability to serve asan sCell 24 for the wireless device 22, e.g., without first obtainingany signal quality measurement, such as an inter-frequency layer 3 (L3)measurement. By not requiring the wireless device 22 to make an L3measurement of the potential sCell 24 before selecting the potentialsCell 24, the need for measurement gaps at the wireless device 22 can beavoided. A measurement gap occurs when the wireless device 22temporarily suspends one or more current connections (e.g., a connectionto the pCell 20) in order to make the L3 measurement of the potentialsCell 24. Using measurement gaps to perform the inter-frequencymeasurements for sCell 24 selection will incur 7-15% throughput loss onconfigured cells depending on the gap pattern configured. By blindlyselecting the sCell 24, this throughput loss can be avoided and theincreased power consumption necessary to perform measurements such as L3measurements can be avoided as well, according to some embodiments.

In one embodiment, blindly selecting the sCell 24 includes selecting thesCell 24 from the list of potential sCells 24 based on a randomselection strategy. In another embodiment, blindly selecting the sCell24 includes selecting the sCell 24 from the list of potential sCells 24based on a round-robin strategy. As used herein, a round-robin strategyinvolves selecting sCells 24 in a sequential order. In some embodiments,the list of potential sCells 24 is sorted by frequency of operation.Further, in one embodiment, the round-robin strategy is started in thelist of potential sCells 24 at a position in the list that is differentfrom a position at which a previous iteration of the round-robinstrategy stopped. In one embodiment, the round-robin strategy is startedin the list of potential sCells 24 at a position in the list immediatelysucceeding a position at which a previous iteration of the round-robinstrategy stopped. It is also possible to start the round-robin strategyat a random position in the list of potential sCells 24. In these ways,the sCells 24 selected for the wireless device 22 may be different fromthe sCells 24 selected for other wireless devices 22 and the networknode may avoid retrying sCells 24 that have recently been selected.

In addition, in some embodiments, starting the round-robin strategy at arandom position in the list of potential sCells 24 may be implemented toavoid the problem of load imbalancing. Load imbalancing occurs when arelative few sCells 24 are disproportionately chosen to be configuredfor wireless devices 22, while other potential sCells 24 are not chosen.In the simplest scenario, each wireless device 22 is provided with thesame list of potential sCells 24 and each round-robin strategy isstarted in the list of potential sCells 24 at the same position in thelist. In this scenario, every wireless device 22 for which the firstsCell 24 in the list would be appropriate will configure that sCell 24.Consequently, the sCell 24 that is last in the list will be veryunlikely to be configured as an sCell 24 for a wireless device 22. Thus,the load on the different sCells 24 will be imbalanced. In some cases,this will lead to decreased quality of service for the wireless devices22 configured to use the overused sCell 24, while resources availablefor the less used sCells 24 will not be utilized.

After blindly selecting an sCell 24 for the wireless device 22, thenetwork node configures the wireless device 22 with the selected sCell24 (step 106). In LTE, this configuration is accomplished by sending anappropriate Radio Resource Control (RRC) message to the wireless device22. After configuring the wireless device 22 with the selected sCell 24,the network node determines whether a new sCell 24 needs to be selected(step 108). More specifically, as discussed previously in regard to step104, since the configured sCell 24 was blindly selected, it may not bean acceptable sCell 24 for the wireless device 22. As used herein, ansCell 24 is not an acceptable sCell 24 for the wireless device 22 ifeither the wireless device 22 fails to connect to the sCell 24 or if thewireless device 22 indicates that the signal quality from the sCell 24is insufficient. According to one embodiment, if the network nodedetermines that it should select a new sCell 24 (step 108), the networknode returns to step 104 and blindly selects an sCell 24 for thewireless device 22 from the list of potential sCells 24. Otherwise, thenetwork node ends the sCell 24 selection process.

FIG. 4 illustrates the operation of a network node for selecting one ormore of the sCells 24 for the wireless device 22 and configuring thewireless device 22 with the selected sCell(s) 24 according to oneembodiment of the present disclosure. This embodiment is similar to thatof FIG. 3, but in this embodiment, after configuring the wireless device22 with the selected sCell 24, the network node receives an indicationfrom the wireless device 22 that a neighboring sCell 24 of the selectedsCell 24 is better than the selected sCell 24. As discussed above, thenetwork node obtains a list of potential sCells 24 for the wirelessdevice 22 (step 200), optionally weights the list of potential sCells 24(step 202), blindly selects an sCell 24 for the wireless device 22 fromthe list of potential sCells 24 (step 204), and configures the wirelessdevice 22 with the selected sCell 24 (step 206).

After configuring the wireless device 22 with the selected sCell 24, thenetwork node receives an indication from the wireless device 22 that aneighboring cell of the selected sCell 24 is better than the selectedsCell 24 (step 208). In one embodiment, the indication is an indicationof an A4 event. In the LTE specifications, an A4 event occurs when aneighboring cell of, in this example, the selected sCell 24 becomesbetter than a threshold, which is referred to herein as an A4 threshold.In another embodiment, the indication is an indication of an A6 event.In the LTE specifications, an A6 event occurs when a neighboring cellof, in this example, the selected sCell 24 at the same frequency becomesan offset better than the selected sCell 24. This event was added in LTERel-10 specifically to facilitate carrier aggregation.

Depending on the particular implementation, in response to theindication from the wireless device 22, the network node optionallydeconfigures the selected sCell 24 as an sCell 24 of the wireless device22 (step 210). In LTE, this deconfiguration is accomplished by sendingan appropriate RRC message to the wireless device 22. In thisembodiment, in response to receiving the indication that the neighboringcell is better than the selected sCell 24, the network node configuresthe wireless device 22 with the neighboring cell as an sCell 24 for thewireless device 22 (step 212). This newly configured sCell 24 should beat least as good or better than the previously configured sCell 24. Notethat before configuring the neighboring cell as an sCell 24 of thewireless device 22, the network node may determine whether theneighboring cell satisfies one or more predefined criteria. For example,the network node may first confirm that the neighboring cell isavailable for configuration as an sCell 24 and that one or moreparameters of the neighboring cell match the capabilities of thewireless device 22. This may be done by, e.g., determining whether theneighboring cell is in the list of potential sCells 24 for the wirelessdevice 22.

FIG. 5 illustrates the operation of a network node for selecting one ormore of the sCells 24 for the wireless device 22 and configuring thewireless device 22 with the selected sCell(s) 24 according to anotherembodiment of the present disclosure. This embodiment is similar tothose of FIGS. 3 and 4, but in this embodiment, after configuring thewireless device 22 with the selected sCell 24, the network node receivesan indication that the selected sCell 24 is not an acceptable sCell 24for the wireless device 22. As discussed above, the network node obtainsa list of potential sCells 24 for the wireless device 22 (step 300),optionally weights the list of potential sCells 24 (step 302), blindlyselects an sCell 24 for the wireless device 22 from the list ofpotential sCells 24 (step 304), and configures the wireless device 22with the selected sCell 24 (step 306).

Since the configured sCell 24 was blindly selected, it may not be anacceptable sCell 24 for the wireless device 22. If the network nodereceives an indication from, e.g., the wireless device 22 that theselected sCell 24 is not an acceptable sCell 24 for the wireless device22 (step 308), the network node returns to step 304 and blindly selectsa new sCell 24 for the wireless device 22 from the list of potentialsCells 24. Otherwise, the network node ends the sCell 24 selectionprocess. In one embodiment, the indication from the wireless device 22that the selected sCell 24 is not an acceptable sCell 24 for thewireless device 22 is an indication of an A2 event. In the LTEspecifications, an A2 event occurs when a serving cell, which in thisexample is the selected and configured sCell 24, becomes worse than athreshold, which is referred to herein as an A2 threshold. In anotherembodiment, the indication from the wireless device 22 that the selectedsCell 24 is not an acceptable sCell 24 for the wireless device 22 is anindication that the wireless device 22 failed to connect to the selectedsCell 24.

FIG. 6 illustrates the operation of a network node for selecting one ormore of the sCells 24 for the wireless device 22 and configuring thewireless device 22 with the selected sCell(s) 24 according to anotherembodiment of the present disclosure. As discussed above, the networknode obtains a list of potential sCells 24 for the wireless device 22(step 400), optionally weights the list of potential sCells 24 (step402), blindly selects an sCell 24 for the wireless device 22 from thelist of potential sCells 24 (step 404), and configures the wirelessdevice 22 with the selected sCell 24 (step 406).

After configuring the wireless device 22 with the selected sCell 24, thenetwork node receives from, e.g., the wireless device 22 an indicationthat the selected sCell 24 is not an acceptable sCell 24 for thewireless device 22 (step 408). In one embodiment, the indication fromthe wireless device 22 that the selected sCell 24 is not an acceptablesCell 24 for the wireless device 22 is an indication of an A2 event. Inanother embodiment, the indication from the wireless device 22 that theselected sCell 24 is not an acceptable sCell 24 for the wireless device22 is an indication that the wireless device 22 failed to connect to theselected sCell 24. Instead of immediately selecting a new sCell 24 withwhich to configure the wireless device 22, the network node monitors foran indication from the wireless device 22 that a neighboring cell of theselected sCell 24 is better than the selected sCell 24 (step 410). Inone embodiment, the indication that a neighboring cell of the selectedsCell 24 is better than the selected sCell 24 is an indication of an A4event or an A6 event. Receiving either an indication of an A4 event oran indication of an A6 event alerts the network node to the presence ofan sCell 24 that is acceptable, whereas the currently selected andconfigured sCell 24 is not acceptable.

If the network node receives an indication from the wireless device 22that a neighboring cell of the selected sCell 24 is better than theselected sCell 24 (step 412), the network node configures the wirelessdevice 22 with the neighboring cell that is better than the selectedsCell 24 (step 414). Note that in some embodiments, the network node mayfirst determine that the neighboring cell satisfies one or morepredefined criteria for serving as an sCell 24 of the wireless device22. Otherwise, if the network node does not receive an indication fromthe wireless device 22 that a neighboring cell of the selected sCell 24is better than the selected sCell 24, e.g., within a predefined amountof time, the network node can deduce that there are no appropriatesCells 24 that operate at a frequency that is the same as the frequencyof operation of the currently selected and configured sCell 24. If thisdeduction were not true, the network node would have received anindication from the currently selected and configured sCell 24 that aneighboring cell was better than the selected sCell 24. The network nodethen excludes the potential sCells 24 that operate at a frequency thatis the same as a frequency of operation of the selected sCell 24 (step416).

Next, the network node blindly selects a new sCell 24 for the wirelessdevice 22 from the list of potential sCells 24 excluding the potentialsCells 24 excluded in step 416 (step 418). As discussed above, since thenetwork node has deduced that there are no acceptable sCells 24 with afrequency of operation that is the same as the frequency of operation ofthe previously configured sCell 24, this new selection excludes thosesCells 24. Depending on how many sCells 24 share this frequency ofoperation, this exclusion can decrease the amount of time needed to findan acceptable sCell 24 by not configuring these likely unacceptablesCells 24. After blindly selecting a new sCell 24 for the wirelessdevice 22 in step 418, the network node configures the wireless device22 with the newly selected sCell 24 (step 420). From here, in someembodiments, the process can continue until an acceptable sCell 24 hasbeen selected and configured.

FIG. 7 illustrates the operation of a network node for selecting one ormore of the sCells 24 for the wireless device 22 and configuring thewireless device 22 with the selected sCell(s) 24 according to anotherembodiment of the present disclosure. This embodiment is similar to thatof FIG. 6, but in the embodiment of FIG. 7, one embodiment of around-robin selection scheme is utilized.

First, the network node obtains a list of potential sCells 24, asdiscussed above (step 500). The network node sorts the list of potentialsCells 24 by a frequency of operation of the potential sCells 24 toprovide resulting frequency groups (step 502). Each frequency groupincludes one or more sCells 24 having the same frequency of operationand/or frequency band of operation. The sCells 24 within each frequencygroup can be arranged in any suitable manner. For example, if thenetwork node has further information about a preferred order ofselection for the sCells 24, that information can be used to order thesCells 24 within each frequency group.

After sorting the list of potential sCells 24, the network node mayoptionally weight the list of potential sCells 24 (step 504). Thisweighting serves to make the selection of one or more sCells 24 morelikely and/or to make the selection of one or more sCells 24 lesslikely. In one embodiment, this weighting can include altering the orderof the frequency groups or altering the order of the sCells 24 withineach frequency group. The weighting could also include adding one ormore duplicate entries into the list of potential sCells 24, or anyother suitable method, depending on the implementation of the method.

Next, the network node blindly selects an sCell 24 for the wirelessdevice 22 from the list of potential sCells 24 according to theround-robin selection scheme (step 506). In one embodiment, theround-robin selection scheme is started in the list of potential sCells24 at a position in the list that is different from a position at whicha previous iteration of the round-robin selection scheme for selecting aprevious sCell 24 for the wireless device 22 stopped. In one embodiment,the round-robin strategy is started in the list of potential sCells 24at a position in the list immediately succeeding a position at which aprevious iteration of the round-robin strategy for selecting a previoussCell 24 for the wireless device 22 stopped. In one embodiment, the nextposition in the list to select is maintained as an index of the list ofpotential sCells 24. In this embodiment, the index can be changed torefer to the next sCell 24 in the list of potential sCells 24 after eachblind selection. Starting the selection at a different position in thelist avoids selecting an sCell 24 that may have recently been selectedas an sCell 24 for a wireless device 22.

In some embodiments, the optional list weighting and the method ofblindly selecting the next sCell 24 may be implemented to avoid theproblem of load imbalancing. Load imbalancing was discussed in moredetail above and occurs when relatively few potential sCells 24 aredisproportionately chosen to be configured for the wireless devices 22,while other potential sCells 24 are not chosen. Weighting the list ofpotential sCells 24 allows the problem of load imbalancing to be avoidedby increasing the possibility of choosing potential sCells 24 that arecurrently used less than other potential sCells 24. The converse mayalso be used, where the weighting decreases the possibility of choosingpotential sCells 24 that are currently used more than other potentialsCells 24. These are only some ways in which the list of potentialsCells 24 can be weighted.

Additionally, the method of choosing the next sCell 24 to blindly selectmay be implemented to avoid the problem of load imbalancing. In oneembodiment, if the same or a similar list of potential sCells 24 isobtained for more than one wireless device 22, the method of choosingthe next sCell 24 to blindly select may choose a random sCell 24 fromthe list. In this way, the sCells 24 will be configured by the wirelessdevices 22 in a more balanced way. In an embodiment implementing around-robin selection strategy where the next sCell 24 to blindly selectis the next sCell 24 in the list of potential sCells 24, the startingpoint in the list of potential sCells 24 may be different for differentwireless devices 22. In this way, the sCells 24 will be configured bythe wireless devices 22 in a more balanced way. In another embodiment,the list of potential sCells 24 obtained for one wireless device 22includes sCells 24 that are in an order that is different from an orderof potential sCells 24 in another list of potential sCells 24 obtainedby another wireless device 22. In this way the sCells 24 will beconfigured by the wireless devices 22 in a more balanced way.

After blindly selecting an sCell 24 for the wireless device 22, thenetwork node configures the wireless device 22 with the selected sCell24 (step 508). In this embodiment, after configuring the wireless device22 with the selected sCell 24, the network node receives an indicationthat the selected sCell 24 is not an acceptable sCell 24 for thewireless device 22 (step 510). In one embodiment, the indication fromthe wireless device 22 that the selected sCell 24 is not an acceptablesCell 24 for the wireless device 22 is an indication of an A2 event. Inanother embodiment, the indication from the wireless device 22 that theselected sCell 24 is not an acceptable sCell 24 for the wireless device22 is an indication that the wireless device 22 failed to connect to thesCell 24.

Instead of immediately selecting a new sCell 24 with which to configurethe wireless device 22, the network node monitors for an indication fromthe wireless device 22 that a neighboring cell of the selected sCell 24is better than the selected sCell 24 (step 512). In one embodiment, theindication is an indication of an A4 event or an indication of an A6event. Receiving either an indication of an A4 event or an indication ofan A6 event alerts the network node to the presence of an sCell 24 thatis more acceptable than the currently configured sCell 24.

If the network node receives an indication from the wireless device 22that a neighboring cell of the selected sCell 24 is better than theselected sCell 24 (step 514), the network node configures the wirelessdevice 22 with the neighboring cell that is better than the selectedsCell 24 (step 516). Otherwise, if the network node does not receive anindication from the wireless device 22 that a neighboring cell of theselected sCell 24 is better than the selected sCell 24 (step 514), thenetwork node can deduce that there are no appropriate sCells 24 thatoperate at a frequency that is the same as the frequency of operation ofthe selected sCell 24. If this deduction were not true, the network nodewould have received an indication that a neighboring cell was betterthan the selected sCell 24.

The network node can now exclude the potential sCells 24 that operate atthe same as a frequency of operation as the selected sCell 24. Since thelist of potential sCells 24 is already sorted by a frequency ofoperation of the potential sCells 24 to provide frequency groups,excluding the sCells 24 can be accomplished by selecting a new sCell 24from a different frequency group. In this regard, the network nodeblindly selects a new sCell 24 for the wireless device 22 from a nextfrequency group (step 518). In an embodiment where the next sCell 24 toselect is maintained by an index of the list of potential sCells 24, theindex can be advanced to the first sCell 24 in the next frequency groupin the sorted list of potential sCells 24.

As discussed above, since the network node has deduced that there are noacceptable sCells 24 with a frequency of operation that is the same asthe frequency of operation of the previously configured sCell 24, thisnew selection is an sCell 24 with a frequency of operation that isdifferent from the frequency of operation of the previously configuredsCell 24. After blindly selecting an sCell 24 for the wireless device 22from a different frequency group, the network node configures thewireless device 22 with the newly selected sCell 24 (step 520). In someembodiments, the process continues in this manner until an acceptablesCell 24 has been selected and configured for the wireless device 22.

FIG. 8 illustrates the operation of a network node for selecting one ormore of the sCells 24 for the wireless device 22 and configuring thewireless device 22 with the selected sCell(s) 24 according to anotherembodiment of the present disclosure. In this embodiment, specificimplementation is described which covers many of the embodimentspreviously discussed. For clarity and conciseness, FIG. 8 includesreferences to specific measurement events such as A1, A2, A4, and A6measurement events. This is merely an exemplary implementation of oneembodiment of the current disclosure. In other implementations, othermeasurement events or notifications could be used.

First, the network node obtains a list of potential sCells 24 (step600). After obtaining the list of potential sCells 24, the network nodemay optionally weight the list of potential sCells 24 (step 602). Next,the network node checks if all candidate sCells 24 in the list ofpotential sCells 24 have been eliminated from consideration (step 604).If all candidate sCells 24 in the list of potential sCells 24 have beeneliminated from consideration, the wireless device 22 is currently in alocation without acceptable sCell 24 coverage for the wireless device22. In order to avoid configuring the same potential sCells 24 againwhen the sCells 24 are unlikely to be acceptable, the network node waitsfor a timer T1 to expire (step 606). The timer T1 is set to a predefinedamount of time, which may vary depending on the particularimplementation. In one embodiment, the value of the timer T1 isdetermined as a tradeoff between power usage during sCell 24 selectionand configuration attempts and the desirability of having an acceptablesCell 24 configured for the wireless device 22. In one embodiment, thevalue of the timer T1 is determined based on a mobility of the wirelessdevice 22. For instance, the value of the timer T1 may be inverselyrelated to the mobility of the wireless device 22 since the more mobilethe wireless device 22 is, the more likely the wireless device 22 willenter a location with an acceptable sCell 24. After waiting for thetimer T1 to expire, the network node restarts the sCell selectionprocess at a desired location in the list of potential sCells 24 (whichmay be potentially weighted according to step 602) (step 608). Thenetwork node may restart the sCell selection process from any desiredposition in the list of potential sCells 24. For example, the networknode may restart the sCell selection process at a position in the listof potential sCells 24 at which the sCell selection process waspreviously started before eliminating all of the sCells 24 fromconsideration.

At this point, whether proceeding from step 604 (all candidate sCells 24in the list of potential sCells 24 have not been eliminated fromconsideration) or step 608 (restarting the list), the network nodeblindly selects an sCell 24 for the wireless device 22 from the list ofpotential sCells 24 (step 610). As discussed above, in one embodiment,the blind selection may be according to a round-robin selection scheme.However, other blind selection schemes, e.g., random selection, may beused. After blindly selecting an sCell 24 for the wireless device 22,the network node configures the wireless device 22 with the selectedsCell 24 (step 612).

After configuring the wireless device 22 with the selected sCell 24, thenetwork node determines whether an indication of an A2 event has beenreceived from the wireless device 22 (step 614). In the LTEspecifications, an A2 event occurs when a serving cell, which in thiscase is the selected and configured sCell 24, becomes worse than an A2threshold. Receiving an indication of an A2 event means that theselected and configured sCell 24 is not an acceptable sCell 24 for thewireless device 22. Conversely, if an indication of an A2 event is notreceived, means one of two conditions exist, namely: (1) the selectedand configured sCell 24 is an acceptable sCell 24 for the wirelessdevice 22, or (2) for some reason, the network node has not and will notreceive an indication of any event (A1, A2, A4, or A6) from the wirelessdevice 22 for the selected and configured sCell 24.

In order to determine which of these two conditions exists, if thenetwork node does not receive an A2 event, the network node checkswhether any quality indication has been received from the wirelessdevice 22 regarding the selected sCell 24 (step 616). In one embodiment,the quality indication is an indication of an A1 event, an indication ofan A4 event, or an indication of an A6 event. In the LTE specifications,an A1 event occurs when the selected sCell 24 becomes better than athreshold, which is referred to herein as an A1 threshold.

If the network node does not receive an A2 event, but does receive someother quality indication from the wireless device 22 regarding theselected sCell 24, the selected sCell 24 is considered an acceptablesCell 24 for the wireless device 22. In this case, the network nodeenters a loop where the network node monitors the wireless device 22 todetermine whether the selected and configured sCell 24 subsequentlybecomes non-acceptable or a better neighbor cell becomes available. Morespecifically, in this embodiment, the network node determines whether anindication of an A4 or an A6 event has been received from the wirelessdevice 22 for the selected and configured sCell 24 (step 618). Receivingan indication of either an A4 event or an A6 event alerts the networknode to the presence of a neighboring cell of the currently selected andconfigured sCell 24 that is better than the currently selected andconfigured sCell 24.

If an indication of an A4 event or an A6 event has not been received,the network node determines whether an indication of an A2 event hasbeen received from the wireless device 22 for the currently configuredand selected sCell 24 (step 620). If an indication of an A2 event hasbeen received, the process returns to step 604 and is repeated forselection of a new sCell 24 for the wireless device 22. Notably, at thispoint, the previously selected and configured sCell 24 may bedeconfigured. If an indication of an A2 event has not been received, theprocess returns to step 618. At step 618, if the network node receivesan indication of either an A4 event or an A6 event, the network nodeconfigures the wireless device 22 with the neighboring cell that isbetter than the selected sCell 24 (step 622). In other words, theneighboring cell is selected and configured as a new sCell 24 for thewireless device 22. In some embodiments, the previously selected andconfigured sCell 24 may be deconfigured. From step 622, the processproceeds to step 620 and is performed for the newly selected andconfigured sCell 24 of the wireless device 22.

Returning now to the discussion of steps 614 and 616, if the networknode does receive an indication of an A2 event from the wireless device22 for the selected and configured sCell 24, or if the network node didnot receive any quality indication from the wireless device 22 regardingthe sCell 24 in step 616, the network node starts a timer T2 (step 624).In one embodiment, the timer T2 is intended to allow for moreinformation about the configured sCell 24 to be received from thewireless device 22. As with the previously described timer T1, theduration of the timer T2 may be implementation-specific. A larger valuefor the timer T2 leaves the wireless device 22 configured with anunacceptable sCell 24 for a longer time. In contrast, a smaller valuefor the timer T2 may cause the network node to miss one or moreadditional measurement reports that the wireless device 22 might havesent regarding the selected and configured sCell 24. A balance betweenthese two factors will be implementation-specific and may depend on thenetwork architecture, capabilities of the wireless device 22, or anyother factor.

While the timer T2 is running and before the timer T2 expires, thenetwork node determines whether an indication of either an A4 event oran A6 event has been received from the wireless device 22 for theselected and configured sCell 24 (step 626). If the network nodereceives an indication of either an A4 event or an A6 event, the networknode configures the wireless device 22 with the neighboring cell that isbetter than the selected sCell 24 (step 622). Otherwise, the networknode determines whether an indication of an A1 event has been receivedfrom the wireless device 22 for the currently selected and configuredsCell 24 (step 628). Receiving an indication of an A1 event indicatesthat the sCell 24 is now an acceptable sCell 24 for the wireless device22. If the network node does receive an indication of an A1 event, thenetwork node considers the sCell 24 to now be acceptable, and theprocess proceeds to step 620.

If no measurement reports are received in steps 626 and 628, the networknode determines whether the timer T2 has expired (step 630). If thetimer T2 has not expired, the process returns to step 626 such thatsteps 626 and 628 are repeated to continue to monitor for either an A4or A6 event, or for an A1 event. Once the timer T2 has expired, thenetwork node determines whether an A2 event was received but an A6 eventwas not received (step 632). If an A2 event was received but an A6 eventwas not received, the network node can deduce that there are noappropriate sCells 24 that operate at the same frequency of operation asthe currently selected and configured sCell 24. If this deduction werenot true, there should have been an indication that the neighboring cellwas better than the selected sCell 24. Thus, if an indication of an A2event was received but an indication of an A6 event was not received,the network node excludes the potential sCells 24 that operate at afrequency that is the same as a frequency of operation of the selectedsCell 24 (step 634). In some embodiments where the list of potentialsCells 24 is sorted by frequency of operation of the sCells 24 (e.g., inan embodiment of a round-robin selection strategy), excluding thepotential sCells 24 that operate at a frequency that is the same as afrequency of operation of the selected sCell 24 may involve advancingthe selection process to a point in the list where sCells 24 operatingat a different frequency are located.

Whether or not the network node skips to the next frequency in the listof potential sCells 24, the process returns to step 604, where thenetwork node checks if all candidate sCells 24 in the list of potentialsCells 24 have been eliminated from consideration. The process continuesin this manner.

FIG. 9 is a block diagram of a radio access node 26 (e.g., the basestation 16) according to one embodiment of the present disclosure. Asillustrated, the radio access node 26 includes a baseband unit 28including a processing subsystem 30, memory 32, and a network interface34, and a radio unit 36 including a transceiver 38 connected to one ormore antennas 40. The transceiver 38 generally includes analog and, insome embodiments, digital components for wirelessly sending andreceiving data to and from the wireless devices 22 (not shown). From awireless communications protocol view, the transceiver 38 implements atleast part of Layer 1 (i.e., the Physical or “PHY” Layer).

The processing subsystem 30 generally implements any remaining portionof Layer 1 not implemented by the transceiver 38, as well as functionsfor higher layers in the wireless communications protocol (e.g., Layer 2(data link layer), Layer 3 (network layer), etc.). In particularembodiments, the processing subsystem 30 may comprise, for example, oneor several general-purpose or special-purpose microprocessors or othermicrocontrollers programmed with suitable software and/or firmware tocarry out some or all of the functionality of the base station 16described herein. In addition or alternatively, the processing subsystem30 may comprise various digital hardware blocks (e.g., one or moreApplication Specific Integrated Circuits (ASICs), one or moreoff-the-shelf digital and analog hardware components, or a combinationthereof) configured to carry out some or all of the functionality of thebase station 16 described herein. Additionally, in particularembodiments, the above-described functionality of the radio access node26 may be implemented, in whole or in part, by the processing subsystem30 executing software or other instructions stored on a non-transitorycomputer-readable medium such as, for example, the memory 32 or anyother suitable type of data storage component(s).

FIG. 10 is a block diagram of a wireless device 22 according to oneembodiment of the present disclosure. As illustrated, the wirelessdevice 22 includes a radio subsystem 42 including a transceiver 44connected to one or more antennas 46, a processing subsystem 48, andmemory 50. The transceiver 44 generally includes analog and, in someembodiments, digital components for wirelessly sending and receivingdata to and from the base station 16 and the RRHs 18 (shown in FIG. 2).From a wireless communications protocol view, the transceiver 44implements at least part of Layer 1 (i.e., the Physical or “PHY” Layer).

The processing subsystem 48 generally implements any remaining portionof Layer 1 not implemented by the radio subsystem 42, as well asfunctions for higher layers in the wireless communications protocol(e.g., Layer 2 (data link layer), Layer 3 (network layer), etc.). Inparticular embodiments, the processing subsystem 48 may comprise, forexample, one or several general-purpose or special-purposemicroprocessors or other microcontrollers programmed with suitablesoftware and/or firmware to carry out some or all of the functionalityof the wireless device 22 described herein. In addition oralternatively, the processing subsystem 48 may comprise various digitalhardware blocks (e.g., one or more ASICs, one or more off-the-shelfdigital and analog hardware components, or a combination thereof)configured to carry out some or all of the functionality of the wirelessdevice 22 described herein. Additionally, in particular embodiments, theabove-described functionality of the wireless device 22 may beimplemented, in whole or in part, by the processing subsystem 48executing software or other instructions stored on a non-transitorycomputer-readable medium, such as the memory 50 or any other suitabletype of data storage component(s).

FIG. 11 is a block diagram of a radio access node 26 for configuring awireless device 22 (not shown) with an sCell 24 (not shown) according toone embodiment of the present disclosure. As illustrated, the radioaccess node 26 includes a list obtaining module 52, a blind selectionmodule 54, and a configuration module 56 that are each implemented insoftware that, when executed by a processor of the radio access node 26,causes the radio access node 26 to operate according to any one of theembodiments described herein. The list obtaining module 52 operates toprovide the functionality of the radio access node 26 with respect tosteps 100, 200, 300, 400, 500, or 600 described above. Likewise, theblind selection module 54 operates to provide the functionality of theradio access node 26 with respect steps 104, 204, 304, 404, 418, 506,518, or 610 described above. The configuration module 56 operates toprovide the functionality of the radio access node 26 with respect tosteps 106, 206, 210, 212, 306, 406, 414, 420, 508, 516, 520, 612, or 620described above.

In one embodiment, a computer program including instructions which, whenexecuted by at least one processor, causes the at least one processor tocarry out the functionality of the radio access node 26 according to anyone of the embodiments described herein. In one embodiment, a carriercontaining the aforementioned computer program product is provided. Thecarrier is one of an electronic signal, an optical signal, a radiosignal, or a computer-readable storage medium (e.g., a non-transitorycomputer-readable medium such as the memory 32 shown in FIG. 9).

While the embodiments described herein provide numerous advantages, insome example implementations, at least some of the embodiments providethe advantage of configuring a wireless device 22 with an sCell 24 thatis blindly selected, eliminating the need for measurement gaps that cancause a lack of throughput. Note, however, that this advantage is justan example and is not intended to limit the scope of the embodimentsdisclosed herein.

The following acronyms are used throughout this disclosure.

-   -   3GPP 3^(rd) Generation Partnership Project    -   ASIC Application Specific Integrated Circuit    -   CC Component Carrier    -   eNB evolved Node B    -   L3 inter-frequency Layer 3    -   LTE Long Term Evolution    -   LTE Rel-8 Long Term Evolution Release 8    -   LTE Rel-10 Long Term Evolution Release 10    -   MHz Megahertz    -   PCC Primary Component Carrier    -   pCell Primary Cell    -   RRC Radio Resource Control    -   RRH Remote Radio Head    -   RSRP Reference Signal Received Power    -   SCC Secondary Component Carrier    -   sCell Secondary Cell

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present disclosure. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

What is claimed is:
 1. A method of operating a network node comprising:obtaining a list of potential secondary cells for a wireless device;blindly selecting a secondary cell for the wireless device from the listof potential secondary cells; and configuring the wireless device withthe selected secondary cell.
 2. The method of claim 1 wherein blindlyselecting the secondary cell comprises selecting the secondary cell fromthe list of potential secondary cells based on a round-robin strategy.3. The method of claim 2 wherein blindly selecting the secondary cellfrom the list of potential secondary cells based on the round-robinstrategy comprises starting the round-robin strategy in the list ofpotential secondary cells at a position in the list of potentialsecondary cells that is different from a position at which a previousiteration of the round-robin strategy for selecting a previous secondarycell stopped.
 4. The method of claim 2 wherein blindly selecting thesecondary cell from the list of potential secondary cells based on theround-robin strategy comprises starting the round-robin strategy in thelist of potential secondary cells at a position in the list of potentialsecondary cells immediately succeeding a position at which a previousiteration of the round-robin strategy for selecting a previous secondarycell stopped.
 5. The method of claim 1 wherein blindly selecting thesecondary cell comprises selecting the secondary cell from the list ofpotential secondary cells based on a random selection strategy.
 6. Themethod of claim 1 further comprising: receiving an indication from thewireless device that a neighboring cell of the selected secondary cellis better than the selected secondary cell; and in response to receivingthe indication, configuring the wireless device with the neighboringcell as a secondary cell for the wireless device.
 7. The method of claim6 further comprising deconfiguring the selected secondary cell as asecondary cell for the wireless device.
 8. The method of claim 6 whereinthe indication is an indication of an A4 event.
 9. The method of claim 6wherein the indication is an indication of an A6 event.
 10. The methodof claim 1 further comprising: after configuring the wireless devicewith the selected secondary cell, receiving an indication from thewireless device that the selected secondary cell is not an acceptablesecondary cell for the wireless device, and in response: blindlyselecting a new secondary cell for the wireless device from the list ofpotential secondary cells for the wireless device; and configuring thewireless device with the new secondary cell selected for the wirelessdevice.
 11. The method of claim 10 further comprising deconfiguring theselected secondary cell as a secondary cell for the wireless device. 12.The method of claim 10 wherein the indication is an indication of an A2event.
 13. The method of claim 1 further comprising: after configuringthe wireless device with the selected secondary cell, receiving anindication from the wireless device that the selected secondary cell isnot an acceptable secondary cell for the wireless device, and inresponse: monitoring for an indication from the wireless device that aneighboring cell of the selected secondary cell is better than theselected secondary cell; if the indication that the neighboring cell ofthe selected secondary cell is better than the selected secondary cellis not received within a defined period of time, blindly selecting a newsecondary cell for the wireless device from the list of potentialsecondary cells for the wireless device excluding potential secondarycells that operate at a frequency that is the same as a frequency ofoperation of the selected secondary cell; and configuring the wirelessdevice with the new secondary cell selected for the wireless device. 14.The method of claim 13 wherein receiving the indication from thewireless device that the selected secondary cell is not an acceptablesecondary cell for the wireless device comprises receiving an indicationof an A2 event from the wireless device, and monitoring for theindication from the wireless device that the neighboring cell of theselected secondary cell is better than the selected secondary cellcomprises monitoring for an indication selected from the groupconsisting of an indication of an A4 event and an indication of an A6event.
 15. The method of claim 1 wherein the list of potential secondarycells is sorted by a frequency of operation of the potential secondarycells to thereby provide a plurality of frequency groups within thelist, blindly selecting the secondary cell comprises blindly selectingthe secondary cell from one frequency group according to a round-robinstrategy, and the method further comprises: after configuring thewireless device with the selected secondary cell, receiving anindication from the wireless device that the selected secondary cell isnot an acceptable secondary cell for the wireless device; and inresponse: monitoring for an indication from the wireless device that aneighboring cell of the selected secondary cell is better than theselected secondary cell; if the indication that the neighboring cell ofthe selected secondary cell is better than the selected secondary cellis not received within a defined period of time, blindly selecting a newsecondary cell for the wireless device from a next frequency group inthe list of potential secondary cells according to the round-robinstrategy; and configuring the wireless device with the new secondarycell selected for the wireless device.
 16. The method of claim 1 furthercomprising: after configuring the wireless device with the selectedsecondary cell, monitoring for at least one indication from the wirelessdevice selected from the group consisting of: an indication that theselected secondary cell is an acceptable secondary cell for the wirelessdevice; an indication that the selected secondary cell is not anacceptable secondary cell for the wireless device; and an indicationfrom the wireless device that a neighboring cell of the selectedsecondary cell is better than the selected secondary cell; if the atleast one indication is not received within a defined period of time,blindly selecting a new secondary cell for the wireless device from thelist of potential secondary cells for the wireless device; andconfiguring the wireless device with the new secondary cell selected forthe wireless device.
 17. The method of claim 1 wherein obtaining thelist of potential secondary cells comprises determining the list basedon an intersection of cells available to be configured as a secondarycell and capabilities of the wireless device.
 18. The method of claim 17wherein determining the list based on the intersection of the cellsavailable to be configured as a secondary cell and the capabilities ofthe wireless device comprises determining the list based on anintersection of a frequency of operation of the cells available to beconfigured as a secondary cell and frequency capabilities of thewireless device.
 19. The method of claim 1 wherein the list of potentialsecondary cells for the wireless device comprises potential secondarycells in an order that is different from an order of potential secondarycells comprised in a second list of potential secondary cells for asecond wireless device.
 20. The method of claim 1 further comprisingweighting the list of potential secondary cells before blindly selectingthe secondary cell.
 21. The method of claim 20 wherein weighting thelist of potential secondary cells before blindly selecting the secondarycell comprises adding one or more duplicate entries into the list ofpotential secondary cells.
 22. The method of claim 20 wherein weightingthe list of potential secondary cells before blindly selecting thesecondary cell comprises adjusting a probability of selection for one ormore entries in the list of potential secondary cells.
 23. The method ofclaim 1 wherein the network node comprises a radio network node.
 24. Themethod of claim 23 wherein the radio network node comprises a basestation.
 25. A network node for configuring a wireless device with asecondary cell comprising a processor and a memory, the memorycontaining instructions executable by the processor, whereby the networknode is operative to: obtain a list of potential secondary cells for thewireless device; blindly select a secondary cell for the wireless devicefrom the list of potential secondary cells; and configure the wirelessdevice with the selected secondary cell.